The use of multiple transmit and receive antennas can enable very large increases in the capacity—defined as the throughput or bit rate that can be reliably conveyed—of wireless communication systems. For a given set of transmit and receive antennas, the highest capacity is attained when the transmit signal in the multiple antenna wireless links is optimized. This is straightforward when both the transmitter and the receiver can track the instantaneous state of the radio channel between them. Such tracking is fairly simple at the receiver, but very challenging at the transmitter, particularly in mobile systems, because of the fast-changing nature of the channel. Namely, by the time the receiver can report the instantaneous state of the channel to the transmitter such that the transmitter can adapt to the instantaneous state, the instantaneous state has changed. Hence, it is often the case that the transmitter must operate without up-to-date reliable information about the instantaneous response of the channel, and sub-optimal covariance and thus capacity is achieved.